Preparation of hydrocarbon silanes from polysilanes

ABSTRACT

Polysilanes having methyl and/or chlorine attached to the silicon atom are reacted with hydrocarbon halides in the presence of tertiary amines or their halide salts or quaternary ammonium or quaternary phosphonium halides to give hydrocarbon chloro monosilanes. For example, allyl chloride is reacted with hexachlorodisilane in the presence of tetrabutyl phosphonium chloride to give allyl trichlorosilane. ATOMS.

United States Patent Atwell et al.

[ 1 Apr. 15, 1975 PREPARATION OF HYDROCARBON SILANES FROM POLYSILANES Inventors: William H. Atwell; Gary N.

Bokerman, both of Midland, Mich.

Assignee: Dow Corning Corporation, Midland,

Mich.

Filed: July 30, 1973 App]. No.: 383,758

U.S. Cl. 260/4482 E; 260/448.2 D; 260/4482 P; 260/4488 R int. Cl (:07: 7/08; C07f 7/12 Field of Search... 260/448.2 B, 448.2 P, 448.2 D, 260/4488 R References Cited UNITED STATES PATENTS 10/1967 Harding et al. 260/4482 E OTHER PUBLICATIONS Banford et al., lnorg. Nacl. Chem. Letters, 8(8), pp. 733-736, (1972), Pergamon Press.

Primary ExaminerPaul F. Shaver Attorney, Agent, or Firm-Robert F. Fleming, Jr.

[57] ABSTRACT Polipilanes having methyl and/or chlorine attached to the silicon atom are reacted with hydrocarbon halides in the presence of tertiary amines or their halide salts or quaternary ammonium or quaternary phosphonium halides to give hydrocarbon chloro monosilanes. For example, allyl chloride is reacted with hexachlorodisilane in the presence of tetrabutyl phosphonium chloride to give allyl trichlorosilane.

6 Claims, No Drawings PREPARATION OF HYDROCARBON SILANES FROM POLYSILANES .lt is known from US. Pat. No. 2,474,087 that hydrocarbon halides canbe reacted with hexachlorodisilane without a catalyst to produce hydrocarbon halosilanes. The patent also teaches that, if desired, cuprous chloride, antimony trichloride, or mercuric chloride can be employed as catalysts. However, all the examples in the pat ent show reaction temperatures ranging from 200 to 350C.

It is also known from Us. Pat. No. 2,709,176 that one can react polysilanes with hydrogen chloride in the presence of tertiary amines or their halide salts to give silanes having higher SiH content than the starting material. However, this reaction does not establish any new silicon-carbon .bonds but merely establishes silicon-hydrogen and silicon-chlorine bonds.

It is also known from U.S.'Pat. Nos. 2,598,435 and 2,842,580 that rearrangement of methyl and chlorine substituted polysilanes can be carried out to produce monomeric silanes and polysilanes having a greater number of silicon atoms than the starting polysilane. This is particularly taught in column 3, line 20, of US. Pat. No. 2,842,580. The former of these two patents teaches this rearrangement in the. absence of a catalyst and the latter teaches that it can be carried out in the presence of quaternary ammonium halides, or quaternary phosphonium halides. However, in this reaction one builds up a residue of polysilanes which in themselves are of no commercial utility. Also no new carbon-silicon--bonds* are formed in this reaction and there is no suggestion that the quaternary ammonium halides or phosphonium halides would be catalysts for the reaction of hydrocarbon halides with polysilanes. *Except by rearrangement.

lt is the object of this invention to carry out the reaction of hydrocarbon halides with polysilanes in a manner which is more economically feasible than that shown in US. Pat. No. 2,474,087; namely at a lower temperature and in better yields. It is also the object of this invention to be able to utilize polysilane residues which occur from the reaction of methyl chloride with silicon and from the reaction of hydrogen chloride with silicon to produce more commercially valuable materials. It is a further object to carry out this reaction without producing silicon hydrides which although usable, are often not desirable. Finally it is an object of this invention to carry out the aforesaid reaction with the production primarily of hydrocarbon substituted monosilanes and silicon tetrachloride both of which are commercially usable materials.

This invention relates to a method of reacting (l) RCl with (2) Me,Cl,,Si to produce RMe,SiCl the improvement comprising carrying out the reaction in contact with a catalytic amount of a catalyst of the group consisting of R N, R' N.HCl, R',NC1 and R' PCl at a temperature from 30 to 250C. in which R is an alkyl radical of from 1 to 18 carbon atoms, an

alkenyl radical of from 2 to 18 carbon atoms, or an aralkyl radical'of from 7 to 18 carbon atoms,

A isto 2, i v

y is l to 3,

the sum of x and y being from 1.5 to 3, all the silicon atoms in (2) beingbonded to at least one other silicon atom and all the valences of the silicon atoms ried out in the presence or absence of a solvent. Thus,

the amount of solvent employed, if desired, is not critical and the primary purpose of the solvent is to facilitate handling of the reaction mixture. If employed, the

solvents are those which do not react with chloro silanes and can be any such solvent such as hydrocarbons, such as benzene, toluene, pentane, and the like, or any halohydrocarbon such as chlorobenzene, or chlorotoluene; ethers such as dibutyl ether, or the dimethyl ether of ethylene glycol; or nitriles such as acetonitrile.

The polysilanes employed in this invention can be prepared by any conventional means known in the art. For one they are by-produced in the commercial reaction of methyl chloride with silicon to form methylchlorosilanes. In this process, most of the polysilanes employed have some methyl groups substituted on the silicon atoms. Hexachlorodisilane and polysilanes containing only chlorine are by-produ'ced in the commercial process of reacting hydrogen chloride with silicon to produce trichlorosilane. For the purpose of this invention, one can first isolate individual species of the silanes and then react them in the process of this invention or one can merely use the residue from the aforesaid commercial processes.

Operative examples of silanes are 'disilanes such as hexachlorodisilane, l,2-dimethyltetrachlorodisilane, l ,1-dimethyltetrachlorodisilane, l,l,2,2-tetramethyldichlorodisilane; polymeric silanes having more than two silicon atoms such as I Cl SiSiSiC1 or branched complicated structures having the empirical formula Cl Si, Cl Si, or Me Cl, Si. Thus, (2) can vary from dimeric materials to high polymeric materials.

The basic reaction involved is the cleavage of the silicon-silicon bond to establish a silicon-carbon bond and a new silicon-chlorine bond. Although the exact mechanism for this reaction i'shot clearly understood and is undoubtedly quite complicated, the overall effect is the above reaction. Thus, the products of this invention are monomeric materials of the formula RMe SiCland silicon tetrachloride.

The hydrocarbon halides employed in this invention can be those in which R is any alkyl radical of from 1 to 18 carbon atoms such as methyl, ethyl, isopropyl, tbutyl, octyl, or octadecyl, or any alkenyl radical of 2 to 18 carbon atoms, such as allyl, methallyl, hexenyl, octenyl, or octadecenyl, andiany aralkyl radical of 7 to l8 carbon atoms, suchas benzyl, beta-phenylethyl, beta-phenylpropyl, omega-phenyldodecyl, betanaphthylethyl, gamma xenylpropyl, tolylmethyl, and p-vinylbenzyl. i

As can be seen, the catalysts employed in this invention are tertiary amines. their chloride salts, quaternary ammonium chlorides and quaternary phosphonium chlorides. Any of these materials can be employed in mol of disilane. The mixture was then heated as indicated in a closed container and the progress of the reaction was followed by g.l.c. The solvent used in Runs 1 to 6 and 9 to 1 l was benzene and that used in Runs this invention in which R is any alkyl radical of from 7, 8 and '12 to 15 was o-dichlorobenzene.

Reaction Conditions Run Weight Organic Weight Weight Temperature No. Silane in g. Halide in g. Catalyst in g. C. Time Yield Product 1 Si Cl, 10.8 C H Cl 3.27 NPr 0.284 75 96 hr. 70% C,,H SiCl 3 Si- ,Cl,; 10.8 C;,H -,Cl 3.06 HNBu Cl 0.439 75 115 hr. 81% C H SiCl 4 Si Cl 4.60 C H Cl 1.31 Bu.,NC1 0.238 75 12 hr. 80% C H SiCl 6 Si Cl 5.9 C H Cl 1.7 None 75 l 15 hr. trace C H SiCL,

7 Si- CL, 10.8 C.,H Cl 3.70 Bu NCl 0.566 100 140 hr. 46% C H SiCl 8 Si Cl 10.8 C H,,Cl 3.7 None 125 26 hr. None 9 Si Cl,-, 23.8 PhCH Cl l 1.3 Bu PCl 1.31 75 22 hr. 87% PhCH,SiCl, 10 Si C1 23.8 PhCHgCi 1 1.3 None 75 24 hr. None 1 1 Si Cl 4.48 MeCl 55 psi Bu PCl 0.83 100 46 hr. 86% MeSiCl: 12 Me Si Cl 4.42 C H Cl 1.48 Bu NCl 0.280 125 30 hr. 70% C H MeSiCl 13 Me Si C 4 4.42 C H C1 1.48 None 125 77 hr. None 14 Me Si,Cl;, 3.16 C;,H Cl 1.17 Bu PCl 0.226 125 l 14 hr. 27% C H MeSiCl 15 Me;,Si Cl 3.16 C H Cl 1.17 None 125 200 hr. trace C H MeSiCl M01 '14 based on mols of starting silane.

l to 18 carbon atoms, such as methyl, ethyl, butyl, propyl, isopropyl, t-butyl, octyl, dodecyl, or octadecyl. and any aralkyl radical of from 7 to 18 carbon atoms such as benzyl, beta-phenylpropyl, beta-phenylethyl, tolylmethyl, xenylethyl, beta-naphthylethyl, or omegaphenylhexyl.

The amount of catalyst employed in this invention is not critical as long as there is a catalytic amount present. A catalytic amount" is that amount required to substantially enhance the rate of the reaction over that obtained with no catalyst present. The preferred range is from 0.01 to 10 percent by weight based on the total weight of reactants (l) and (2).

The following examples are illustrative only and should not be construed as limiting the invention which is properly delineated in the appended claims. Analysis of the reaction products was carried out by gas liquid chromatography (g.l.c.

EXAMPLE 1 10.67 g. of Si Cl was mixed with 3.37 g. of methylene chloride and 0.29 g. of tri-n-propylamine catalyst was added with stirring. The mixture was allowed to disproportionate for 90 hours at room temperature. The methylene dichloride and silicon tetrachloride were removed at reduced pressure.

The residue was a mixture of the amine and polysilanes having 3 or more silicon atoms per molecule and on the average less than 3 chlorine atoms per silicon atom. To this mixture was added 3 ml. of the dimethyl ether of ethylene glycol and 3 ml. of allyl chloride. The mixture was reacted 42 hours at 85C. At the end of this time, most of the allyl chloride was consumed and the only observable product by g.l.c. was allyl trichlorosilane.

EXAMPLE 2 In each case shown below the silanes employed were distilled materials. The indicated quantity of disilane was mixed with the indicated hydrocarbon halide and the specified solvent in amount of 1 mol of solvent per 1n the table, Runs 6, 8, l0, l3 and 15 were made without catalyst for comparison. In the table, the following abbreviations are used: Pr for propyl; Bu for butyl; Ph

for phenyl; and Me for methyl.

EXAMPLE 3 The silane used in this example was the residue obtained by reacting hydrogen chloride with silicon and then removing the trichlorosilane and lower boiling materials. The residue was a liquid composed of hexachlorodisilane and higher silanes.

125.5 g. of this residue and 52.3 g. of allyl chloride were mixed with 100 g. of orthodichlorobenzene and 2.3 g. of benzene and 2.37 g. of triethylamine was slowly added with stirring. The mixture was then heated at 60 to 80C. for 24 hours. At the end of this time the mixture was distilled and there was obtained a 46 percent by weight yield of allyltrichlorosilane based on the weight of the silane residue.

For a comparison, the reaction was run with no catalyst. A mixture of 35.2 g. of residue, 27.0 g. o-

dichlorobenzene and 9.9 g. of allyl chloride was heated. at C. for 24 hours and only 7 percent by weight yield of the desired allyl trichlorosilane was obtained.

EXAMPLE 4 Hydrocarbon Halide Silane isopropyl chloride isopropyltrichlorosilane octyl chloride octyltrichlorosilane dodecyl chloride dodecyltrichlorosilane octadecyl chloride octadecyltrichlorosilane methallyl chloride methallyltrichlorosilane B-phenylethyl chloride fi phenylethyltrichlorosilane B-phenylpropyl chloride fi-phenylpropyltrichlorosilane p-methylbenzyl chloride p-tolyltrichlorosilane octenyl chloride octenyltrichlorosilane EXAMPLE 5 When allyl chloride is reacted with hexachlorodisilane in the presence of 5 percent by weight of the following catalysts at 150C. for 100 hours. allyltrichlorosilane is obtained. The catalysts are:

to produce RMe,SiCl the improvement comprising carrying out the reaction in contact with a catalytic amount of a catalyst of the group consisting of R' N,

R -,N.HCl. R' NCl and R' PCl at a temperature of from 30 to 250C. in which R is an alkyl radical of from I to 18 carbon atoms, an

alkenyl radical of 2 to 18 carbon atoms, or an am]- kyl radical of from 7 to 18 carbon atoms, is O to 2, y is l to 3, the sum of .r v being from 1.5 to 3, all the silicon atoms in (2) being bonded to at least one other silicon atom and all the valences of the silicon atoms in (2) being satisfied by other silicon atoms, Cl or Me radicals, and R is an alkyl or aralkyl radical of from 1 to l8 carbon atoms. 2. The process of claim 1 in which the catalyst is the defined quaternary ammonium chlorides.

3. The process of claim 1 in which the catalyst is the defined quaternary phosphonium chlorides.

4. The process of claim 1 in which (1) is allyl chloride.

5. The process of claim 1 in which l is allyl chloride and the catalyst is tetrabutyl ammonium chloride.

6. The process of claim 1 in which l is allyl chloride and the catalyst is tetrabutyl phosphonium chloride. 

2. The process of claim 1 in which the catalyst is the defined quaternary ammonium chlorides.
 3. The process of claim 1 in which the catalyst is the defined quaternary phosphonium chlorides.
 4. The process of claim 1 in which (1) is allyl chloride.
 5. The process of claim 1 in which (1) is allyl chloride and the catalyst is tetrabutyl ammonium chloride.
 6. The process of claim 1 in which (1) is allyl chloride and the catalyst is tetrabutyl phosphonium chloride. 